Image processing apparatus, image processing system and method for processing image

ABSTRACT

According to one embodiment, an image processing apparatus includes an image block generator, a pixel extractor, a correction parameter calculator and a corrector. The image block generator enlarges an image block including a plurality of pixels to generate an enlarged image block. The pixel extractor extracts a maximum pixel with a maximum pixel value and a minimum pixel with a minimum pixel value from the image block. The correction parameter calculator calculates a correction parameter including a first difference and a second difference. The first difference is an absolute value of a difference between a sample pixel value of a sample pixel to be corrected in the enlarged image block and the maximum pixel value. The second difference is an absolute value of a difference between the sample pixel value and the minimum pixel value. The corrector corrects the enlarged image block using the correction parameter.

CROSS REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority fromthe prior Japanese Patent Application No. 2010-259917, filed on Nov. 22,2010, the entire contents of which are incorporated herein by reference.

FIELD

The present invention relates to an image processing apparatus, an imageprocessing system and a method for processing image.

BACKGROUND

Ordinarily, when an image is enlarged, the enlarged image blurs becausethe area of the image increases. In order to improve quality of theenlarged image, methods (e.g., an un-sharp masking process and asharpening tap filter process) in which the outline of the enlargedimage is enhanced to sharpen the enlarged image are known.

However, the degree of sharpening process is increased when sharpeningthe enlarged image. Therefore, the consumption of a memory is alsoincreased while the sharpening process. Additionally, noise such asovershoot and undershoot may arise in proportion to the degree ofsharpness in the sharpening process. As a result, noise increases withthe degree of sharpness.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of the configuration of an image processingsystem 1 of the embodiments.

FIG. 2 is a block diagram of the configuration of an image processingapparatus 10 a of the embodiments.

FIG. 3 is a flowchart illustrating the procedure for a correctionoperation of the first embodiment.

FIG. 4 is a schematic view of the image block BLK of the firstembodiment.

FIG. 5 is a schematic view illustrating an example of an enlarged imageblock BLK′ of the first embodiment.

FIG. 6 is a flowchart illustrating the procedure (S304) for calculatingcorrection parameter of the first embodiment.

FIG. 7 is a flowchart illustrating the procedure for extracting pixel ofthe second embodiment.

FIG. 8 is a schematic view illustrating an image block BLK including anobjective area OA of the second embodiment.

FIG. 9 is a diagram illustrating calculating correlation of the secondembodiment.

FIG. 10 is a flowchart illustrating the procedure for extracting pixelof the third embodiment.

FIG. 11 is a schematic view of the image block BLK divided into the edgearea EA and the smooth area SA in the third embodiment.

FIG. 12 is a flowchart illustrating the procedure for extracting pixelof the third embodiment.

FIGS. 13 to 15 are diagrams for extracting edge pixel of the thirdembodiment.

DETAILED DESCRIPTION

In general, according to on embodiment, an image processing apparatusincludes an image block generator, a pixel extractor, a correctionparameter calculator and a corrector. The image block generator enlargesan image block comprising a plurality of pixels to generate an enlargedimage block. The pixel extractor extracts a maximum pixel with a maximumpixel value and a minimum pixel with a minimum pixel value from theimage block. The correction parameter calculator calculates a correctionparameter including a first difference and a second difference. Thefirst difference is an absolute value of a difference between a samplepixel value of a sample pixel to be corrected in the enlarged imageblock and the maximum pixel value. The second difference is an absolutevalue of a difference between the sample pixel value and the minimumpixel value. The corrector corrects the enlarged image block using thecorrection parameter.

Embodiments will now be explained with reference to the accompanyingdrawings. FIG. 1 is a block diagram of the configuration of an imageprocessing system 1 of the embodiments. FIG. 2 is a block diagram of theconfiguration of an image processing apparatus 10 a of the embodiments.

The image processing system 1 processes image data and displays an imagecorresponding to the image data. The image processing system 1 includesa processor 10, a memory 20, and a display 50. The image processingsystem 1 is implemented in a mobile terminal such as a mobile phone. Theprocessor 10 is connected to the memory 20 and the display 50. Further,the image processing system 1 includes, for example, an imagingapparatus 30 and a communicating apparatus 40 as an inputting devicethat inputs the image data. The communicating apparatus 40 is connectedto a network 60 such as a wired network or a wireless network.

The processor 10 is a semiconductor integrated circuit that executes animage processing program stored in the memory 20 to realize the imageprocessing apparatus 10 a. For example, the processor 10 may be aCentral Processing Unit (CPU). For example, the image processingapparatus 10 a enlarges the image. The memory 20 is a semiconductormemory device such as a flash memory which can store image processingprograms and various pieces of data including image data including aplurality of pixels. The memory 20 can be read by a computer. Theimaging apparatus 30 picks up the image of an object to generate theimage data. For example, the imaging apparatus 30 may be a digitalcamera. The communicating apparatus 40 transfers and receives variouspieces of data via the network 60. For example, the communicatingapparatus 40 may be a network interface for the network60 such as amobile phone network. The display 50 displays the image corresponding toimage data corrected by the processor 10. For example, the display 50may be a Liquid Crystal Display (LCD).

The image processing apparatus 10 a includes an enlarged image blockgenerator 12, a pixel extractor 14, a correction parameter calculator16, and a corrector 18. The image processing apparatus 10 a applies apredetermined enlarging process to an image block BLK generated by avideo decoder 11 and supplies the image block BLK to a video encoder 19.The video decoder 11 is decodes the image data IMG to generate the imageblock BLK. The enlarged image block generator 12 enlarges the imageblock BLK. The image extractor 14 extracts a predetermined pixel fromthe image block BLK. The correction parameter calculator 16 iscalculates correction parameters CP(x′, y′) used in a correctionprocess. The corrector 18 corrects an enlarged image block BLK′ usingthe correction parameters CP(x′, y′). The video encoder 19 encodes acorrected image block BLK_(COR) to generate corrected image data IMG′.

First Embodiment

The image processing apparatus 10 a of a first embodiment will now beexplained. The image processing apparatus 10 a of the first embodimentenlarges and sharpens the image data IMG inputted to the imageprocessing system 1. FIG. 3 is a flowchart illustrating the procedurefor a correction operation of the first embodiment.

<Decoding Video (S302)>

The video decoder 11 receives the image data IMG from the memory 20 orthe input apparatus (the imaging apparatus 30 or the communicatingapparatus 40), and decodes the received image data to generate the imageblock BLK including a predetermined number of pixels PX(x, y). Symbols(x, y) represent the coordinates of each of pixels PX in the image blockBLK. Each pixel PX(x, y) has a predetermined pixel value PV(x, y). FIG.4 is a schematic view of the image block BLK of the first embodiment.FIG. 4 illustrates the image block BLK including 4×4 (i.e., 16) pixelsPX.

<Generating Enlarged Image Block (S313)>

The enlarged image block generator 12 enlarges the image block BLK byusing a predetermined method such as a bilinear method or a bicubicmethod to generate an enlarged image block BLK′ including apredetermined number of enlarged pixels PX′(x′, y′). Symbols (x′, y′)represent the coordinates of each of enlarged pixels PX′ in the enlargedimage block BLK′. Each enlarged pixel PX′(x′, y′) has a predeterminedpixel value PV′(x′, y′). FIG. 5 is a schematic view illustrating anexample of an enlarged image block BLK′ of the first embodiment. FIG. 5illustrates the enlarged image block BLK′ including 8×8 (i.e., 64)enlarged image pixels PX′. That is, the enlarged image block BLK′ ofFIG. 5 is generated by enlarging the image block BLK twice.

<Extracing Pixel (S323)>

The pixel extractor 14 extracts a maximum pixel PX_(MAX) having themaximum pixel value a minimum pixel PX_(MIN) having the minimum pixelvalue from the image block BLK.

<Calculating Correction Parameter (S304)>

The correction parameter calculator 16 calculates the correctionparameter CP(x′, y′) including a maximum pixel value PV_(MAX) of theextracted maximum pixel PX_(MAX) and a minimum pixel PV_(MIN) of theextracted minimum pixel PX_(MIN). That is, the correction parameterincludes a range of the pixel value PV′(x′, y′) of an enlarged pixel.The correction parameter CP(x′, y′) is calculated for each sample pixelPX′_(SMP)(x′, y′) to be corrected. The correction parameter CP(x′, y′)is expressed as the product of a correction vector V(x′, y′), a firstcoefficient C1(x′, y′), and a second correction coefficient C2(x′, y′),as shown in Formula 1. Specifically, S304 is carried out according tothe procedure of FIG. 6. FIG. 6 is a flowchart illustrating theprocedure (S304) for calculating correction parameter of the firstembodiment.

CP(x′, y′)=C1(x′, y′)×C2(x′, y′)×V(x′, y′)   (Formula 1)

<Calculating Difference (S602)>

The correction parameter calculator 16 calculates a first differenceD1(x′, y′) that is the absolute value of the difference between thesample pixel value PV′_(SMO)(x′, y′) and the maximum pixel PX_(MAX), anda second difference D2(x′, y′) that is the absolute value of thedifference between the sample pixel value PV′_(SMP)(x′, y′) and theminimum pixel PV_(min), as shown in Formulas 2 and 3.

D1(x′, y′)=|PV′_(SMP)(x′, y′)−PV_(MAX)|  (Formula 2)

D2(x′, y′)=|PV′_(SMP)(x′, y′)−PV_(MIN)|  (Formula 3)

<Calculating Correction Vector (S604)>

The correction parameter calculator 16 calculates a correction vectorV(x′, y′) based on any difference between the second difference D2(x′,y′) and the first difference D1(x′, y′). The correction vector V(x′, y′)is a vector function based on any difference between the seconddifference D2(x′, y′) and the first difference D1(x′, y′). In thisvector function, the direction of the correction is defined by the signof the difference between the second difference D2(x′, y′) and the firstdifference D1(x′, y′) (i.e., by the magnitude relation between thesecond difference D2(x′, y′) and the first difference D1(x′, y′)). Thedegree of correction is defined by the difference between the seconddifference D2(x′, y′) and the first difference D1(x′, y′). For example,the correction vector V(x′, y′) may be a monotone increasing function.

<Calculating First Coefficient (S606)>

The correction parameter calculator 16 calculates the first coefficientC1(x′, y′) including a third difference D3(x′, y′) that is the absolutevalue of the difference between the maximum pixel value PV_(MAX) and theminimum pixel value PV_(MIN). The first coefficient C1(x′, y′) is ascalar function based on the third difference D3(x′, y′). In this scalarfunction, the degree of correction is defined by the third differenceD3(x′, y′). For example, the first coefficient C1(x′, y′) may be amonotone increasing function.

<Calculating Second Coefficient (S608)>

The correction parameter calculator 16 calculates the second coefficientC2(x′, y′) defined by the degree of characteristic of the image blockBLK. The second coefficient C2(x′, y′) is a scalar function based on thedegree of characteristic of the image block BLK. The degree ofcharacteristic of the image block BLK may be detected by the processor10 that analyzes image data IMG or may be defined by predeterminedattribute information (e.g., information indicating a photographic scenewhen the imaging apparatus 30 captures the image data IMG) included inthe image data. For example, the second coefficient C2(x′, y′) may be adifferential coefficient or a constant.

<FIG. 3: Sharpening (S306)>

The corrector 18 adds the correction parameter CP(x′, y′) to the samplepixel value PV_(SMP)(x′, y′) to calculate a corrected pixel valuePV_(COR)(x′, y′), as shown in Formula 4. As a result of S306, acorrected image block BLK_(COR) including the corrected pixels PX_(COR)equal in number to the enlarged pixels PX′ of the enlarged block BLK′can be obtained.

PV_(COR)(x′, y′)=PV_(SMP)(x′, y′)+CP(x′, y′)   (Formula 4)

<FIG. 3: Video Encoding (S308)>

The video encoder 19 encodes the corrected image block BLK_(COR) togenerate corrected image data IMG′ and outputs the generated correctedimage data IMG′ to the communicating apparatus 40 or the display device50.

According to the first embodiment, the enlarged pixel value PV′(x′, y′)in the enlarged image block BLK′ is corrected using the maximum pixelvalue PV_(MAX) and the minimum pixel value PV_(MIN) in the image blockBLK. That is, the sharpening operation is performed using only the imagedata IMG inputted to the image processing system 1. Therefore, thedegree and the times required for the sharpening process can be reduced,and also amount of noise in the corrected image block BLK_(COR) can bereduced. Accordingly, an image without distortion can be displayed.

Incidentally, in S306, when the corrected pixel value PV_(COR)(x′, y′)is greater than the maximum pixel value PV_(MAX), the corrector 18 maychange the corrected pixel value PV_(COR)(x′, y′) to the maximum pixelvalue PV_(MAX). Conversely, when the corrected pixel value PV_(COR)(x′,y′) is smaller than the minimum pixel value PV_(MIN), the corrector 18may change the corrected pixel value PVCOR(x′, y′) into the minimumpixel value PV_(MIN). In other words, in S306, when the corrected imageblock BLK_(COR) includes a pixel having a pixel value out of apredetermined range, the corrector 18 may change the pixel value out ofthe predetermined range into the maximum pixel value PV_(MAX) or theminimum pixel value PV_(MIN). Therefore, the corrected pixel valuePV_(COR)(x′, y′) can be fallen within the range from the minimum pixelvalue PV_(MIN) to the maximum pixel value PV_(MAX). As a result, theexcessive enhancement of contrast can be prevented when an imagecorresponding to the corrected image block BLK_(COR) is displayed.

Second Embodiment

The image processing apparatus 10 a of a second embodiment will now beexplained. The image processing apparatus 10 a of the second embodimentchanges a pixel value of an image block by applying a tap filter to theimage block, and then extracts the maximum pixel or the minimum pixel toperform an operation such as a correction process. For example, the tapfilter is a 2n−1 (n is an integer of 1 or greater) tap filter such as a3-tap filter. Descriptions same as those in the first embodiment willnot be repeated. FIG. 7 is a flowchart illustrating the procedure forextracting pixel of the second embodiment.

<Determing Objective Area (S702)>

The pixel extractor 14 determines an objective area OA in which thepixel in the image block BLK is extracted. For example, the objectivearea OA may include 2×2 pixels and be located around the coordinates(x′, y′) of the sample pixel PX′_(SMP). FIG. 8 is a schematic viewillustrating an image block BLK including an objective area OA of thesecond embodiment. In FIG. 8, the objective area OA includes fourpixels, i.e., pixels PX(2, 2) to PX(3, 3).

<Calculating Correlation (S704)>

The pixel extractor 14 applies the tap filter to a objective pixelPX_(O)(x, y) in the objective area OA to calculate a correlation valueρ(x, y) of the objective pixel PX_(O)(x, y) with the surrounding pixelPX_(P)(xp, yp) that is surrounded by the objective pixel PX_(O)(x, y),and changes the objective pixel value PX_(O)(x, y) into the correlationvalue ρ(x, y). Therefore, the objective pixel value PX_(O) is correctedto a value correlated with the surrounding pixel values PV_(P)(xp, yp).FIG. 9 is a diagram illustrating calculating correlation of the secondembodiment. As shown in FIG. 9, when the 3-tap filter is applied to theobjective pixel PX_(O)(3, 3), the pixel value of the objective pixelPX_(O)(3, 3) is changed into the correlation value ρ(3, 3) of nine (3×3)pixels (i.e., the objective pixel PX_(O)(3, 3) and eight surroundingpixels PX_(P)(2, 2) to PX_(P)(4, 4)) whose center pixel is the objectivepixel PX_(O)(3, 3). S704 is executed for all the objective pixels PX_(O)in the objective area OA.

<Extracting Pixel from Objective Area (S706)>

The pixel extractor 14 extracts the maximum pixel PX_(MAX) and theminimum pixel PX_(MIN) from the objective area OA. When S706 iscompleted, S304 to S308 are carried out as in the first embodiment.

According to the second embodiment, the objective pixel value PX_(O)(x,y) is changed applying the tap filter to the image block, and then themaximum pixel PX_(MAX) and the minimum pixels PX_(MIN) are extractedfrom the objective area OA. Therefore, using one type of process, themaximum pixel PX_(MAX) and minimum pixel PX_(MIN) correlated with theirsurrounding pixels can be extracted irrespective of characteristics ofthe image. Compared to the first embodiment, noise in the correctedimage block BLK_(COR) can be further reduced. Accordingly, an imagewithout distortion can be displayed.

Third Embodiment

The image processing apparatus 10 of a third embodiment will now beexplained. The image processing apparatus 10 a of the third embodimentuses algorithm for an edge area and other algorithm for a smooth areawhen maximum and minimum pixels are extracted from the edge and smoothareas to correct image data. Descriptions identical to those in theembodiments described above will not be repeated. FIG. 10 is a flowchartillustrating the procedure for extracting pixel of the third embodiment.

<Analyzing Image (S1002)>

The pixel extractor 14 divides the image block BLK into an edge area EAand a smooth area SA based on the degree of characteristic of the imageblock BLK. Specifically, the pixel extractor 14 analyzes thecharacteristic of the image block BLK to detect the degree ofcharacteristic of the image block BLK. Based on the detected degree ofcharacteristic, the pixel extractor 14 detects the edge portion or theoutline portion of the image block BLK. The image extractor 14 thendefines the area (i.e., the area where the edge portion or the outlineportion is detected) as the edge area EA, and the area other than theedge area (i.e., the area where neither the edge portion nor the outlineportion is detected) as the smooth area SA. The image extractor 14divides the image block BLK based on the edge area EA and the smootharea SA. FIG. 11 is a schematic view of the image block BLK divided intothe edge area EA and the smooth area SA in the third embodiment. In FIG.11, the area that includes pixels PX(2, 2) to PX(3, 3) is the edge areaEA and the area that not including the pixels PX(2, 2) to PX(3, 3) isthe smooth area SA.

The method for detecting the degree of characteristic of the image blockBLK is an edge detecting method or an outline detecting method. In theedge detecting method, an edge portion with a luminance gradient greaterthan a predetermined threshold is detected using a Sobel filter or aLaplacian filter. In the outline detecting method, an outline portionwith an image of the frequency characteristic correlated with thesurrounding portions of the image among a plurality of edge portions isdetected. It should be noted that the method for detecting the degree ofcharacteristic of the image block BLK is limited to neither the edgedetecting method nor the outline detecting method.

<S1004>

The pixel extractor 14 determines whether the result of the analysis inS1002 is the smooth area SA or not. When the result is the smooth areaSA (S1004—YES), S1006 is carried out. When the result is the edge areaEA (S1004—NO), S1016 is carried out.

<Extracting Smooth Pixel (S1006)>

The pixel extractor 14 extracts a first maximum pixel PX1 _(MAX) havingthe maximum pixel value and a first minimum pixel PX1 _(MIN) having theminimum pixel value from the smooth area SA, as in extracting pixel(FIG. 3) of the first embodiment or as in extracting pixel (FIG. 7) ofthe second embodiment.

<Extracting Edge Pixels (S1016)>

The pixel extractor 14 extracts a second maximum pixel PX2 _(MAX) havingthe maximum pixel value and a second minimum pixel PX2 _(MIN) having theminimum pixel value from the edge area EA. S1016 is carried outaccording to the procedure of FIG. 12. FIG. 12 is a flowchartillustrating the procedure for extracting pixel of the third embodiment.

<Extracting Pixel from Edge Area (S1202)>

The pixel extractor 14 extracts the maximum pixel PX_(MAX) and theminimum pixel PX_(MIN) from the edge area EA. For example, in FIG. 11,the pixel PX(2, 2) is extracted as the maximum pixel PX_(MAX) and thepixel PX(3, 3) is extracted as the minimum pixel PX_(MIN). When S1202 iscompleted, the maximum pixel PX_(MAX) and the minimum pixel PX_(MIN) arerespectively processed.

<Shifting Objective Area for Maximum Pixel (S1204) and ExtractingMaximum Pixel from Objective Area (S1206)>

The pixel extractor 14 shifts the objective area in the directionconnecting the extracted minimum pixel PX_(MIN) and maximum pixelPX_(MAX) (i.e., the direction from the minimum pixel PX_(MIN) to themaximum pixel PX_(MAX)) (S1204). The shifted objective area includes themaximum pixel PX_(MAX). Subsequently, from the shifted objective area,the pixel extractor 14 extracts the maximum pixel PX′_(MAX) among thepixels except for the maximum pixel PX_(MAX) in the pre-shiftedobjective area (S1206).

<S1207 and S1208>

The pixel extractor 14 determines whether the maximum pixel PX′_(MAX) inthe shifted objective area is greater than a maximum reference valuethat is the sum of the maximum pixel value PV_(MAX) in the edge area EAand a predetermined maximum pixel threshold TH_(MAX) (S1207). When themaximum pixel value PV_(MAX) is greater than the maximum reference value(S1207—YES), the pixel extractor 14 determines whether the objectivearea can be shifted or not (S1208). For example, when the shiftedobjective area includes a pixel at the edge of the image block BLK orwhen the number of times that shifting is carried out reaches apredetermined number, it is determined that the objective area cannot beshifted (S1208—NO), and then the flow proceeds to S1209. When it isdetermined that the objective area can be shifted (S1208—YES), the flowreturns to S1204. On the other hand, when the maximum pixel valuePV′_(MAX) is equal to or smaller than the maximum reference value(S1207—NO), the flow proceeds to S1209.

<S1209>

The pixel extractor 14 defines the maximum pixel PX′_(MAX) extractedfrom the shifted objective area as the maximum PX_(MAX), When themaximum pixel value PV′_(MAX) is equal to or smaller than the maximumreference value (S1207—NO), the maximum pixel PX_(MAX) is defined as themaximum pixel for the whole of the image block BLK.

<Shifting Objective Area for Minimum Pixel (S1214) and ExtractingMinimum Pixel from Objective Area (S1216)>

The pixel extractor 14 shifts the objective area in the directionconnecting the extracted maximum pixel PX_(MAX) and the minimum pixelPX_(MIN) (i.e., the direction from the maximum pixel PX_(MAX) to theminimum pixel PX_(MIN)) (S1214). The shifted objective area includes theminimum pixel PX_(MIN). Subsequently, in the shifted objective area, thepixel extractor 14 extracts the minimum pixel PX_(MIN) among the pixelsexcept for the minimum pixel PX_(MIN) in the pre-shifted objective area(S1216).

<S1217 and S1218>

The pixel extractor 14 determines whether the minimum pixel PX_(MIN) inthe shifted objective area is smaller than a minimum reference valuethat is the difference between the minimum pixel PX_(MIN) in the edgearea EA and a predetermined minimum pixel threshold TH_(MIN) (S1217).When the minimum pixel value PV′_(MIN) is smaller than the minimumreference value (S1217—YES), the pixel extractor 14 determines whetherthe objective area can be shifted or not (S1218). For example, when theshifted objective area includes a pixel at the edge of the image blockBLK or when the number of times that shifting is carried out reaches apredetermined number, it is determined that the objective area cannot beshifted (S1218—NO), and then the flow proceeds to S1219. When it isdetermined that the objective area can be shifted (S1218—YES), the flowreturns to S1214. On the other hand, when the minimum pixel valuePV′_(MIN) is equal to or greater than the minimum reference value(S1217—NO), the flow proceeds to S1219.

<S1219>

The pixel extractor 14 defines the minimum pixel PX′_(MIX) extractedfrom the shifted objective area as the minimum PX_(MIX). When theminimum pixel value PV′_(MIN) is equal to or smaller than the minimumreference value (S1217—NO), the minimum pixel PX_(MIX) is defined as theminimum pixel for the whole of the image block BLK.

<S1008>

The pixel extractor 14 determines whether S1006 or S1016 is completedfor all the image blocks BLK (S1008). When it is not completed(S1008—NO), the flow returns to S1002. When it is completed (S1008—YES),extracting pixel is completed. When extracting pixel is completed, S304to S308 are carried out as in the first embodiment.

FIGS. 13 to 15 are diagrams for extracting edge pixel of the thirdembodiment. As shown in FIG. 13, the maximum pixel PX_(MAX)(2, 2) andthe minimum pixel PX_(MIN)(3, 3) are extracted from the edge area EA inS1202. Extracting the maximum pixel and the minimum pixel for all theimages BLK will now be explained.

As shown in FIG. 14, the objective area is shifted in the directionconnecting the minimum pixel PX_(MIN) (3, 3) and the maximum pixelPX_(MAX) (2, 2), that is, the direction from the edge area EA to thearea A_(MAX), in S1204. Subsequently, the maximum pixel PX′_(MAX) (2, 1)is extracted from the area A_(MAX) in S1206. Then, it is determinedwhether the maximum pixel PX′_(MAX) (2, 1) is greater than the maximumreference value or not in S1207. When the maximum pixel PX′_(MAX) (2, 1)is greater than the maximum reference value, it is determined whetherthe objective area can be shifted or not in S1208. In FIG. 14, since thearea A_(MAX) includes pixels PX(1, 1), PX(1, 2), and PX(2, 1) at theedges of the image block BLK, the objective area cannot be shifted fromthe area A_(MAX) to another area. Therefore, the maximum pixel PX′_(MAX)(2, 1) is set as the maximum pixel PX_(MAX) for the image block BLK inS1209.

As shown in FIG. 15, the objective area is shifted in the directionconnecting the maximum pixel PX_(MAX) (2, 2) and the minimum pixelPX_(MIN) (3, 3), that is, from the edge area EA to the area A_(MIN), inS1214. Subsequently, the minimum pixel PX′_(MIN) (4, 3) is extractedfrom the area A_(MIN) in S1216. Next, it is determined whether theminimum pixel PX′_(MIN) (4, 3) is smaller than the minimum referencevalue or not in S1217. When the minimum pixel PX′_(MIN) (4, 3) issmaller than the minimum reference value, it is determined whether theobjective area can be shifted or not in S1218. In FIG. 15, since thearea A_(MIN) includes pixels PX(4, 3), PX(3, 4), and PX(4, 4) at theedges of the image block BLK, the objective area cannot be shifted fromthe area A_(MIN) to another area. Therefore, the minimum pixel PX′_(MIN)(4, 3) is set as the minimum pixel PX_(MIN) for the image block BLK inS1219.

According to the third embodiment, when at least one of the secondmaximum pixel value PV2 _(MAX) and the second minimum pixel value PV2_(MIN) is not included in a predetermined range, at least one of thesecond maximum pixel value PV2 _(MAX) and the second minimum pixel valuePV2 _(MIN) is extracted from the objective area obtained by shifting thearea including at least one of the second maximum pixel value PV2 _(MAX)and the second minimum pixel value PV2 _(MIN) in a predetermineddirection. In the third embodiment, a pixel with a pixel value closer tothe maximum pixel value PV_(MAX) is corrected in the direction of themaximum pixel PX_(MAX), and a pixel with a pixel value closer to theminimum pixel PV_(MIN) is corrected in the direction of the minimumpixel PX_(MIN). On the other hand, a pixel with a pixel value close tothe median between the maximum pixel value PV_(MAX) and the minimumpixel value PV_(MIN) is not corrected. Compared to the first and secondembodiments, noise in the corrected image block BLK_(COR) can be furtherreduced. Accordingly, the image without distortion can be displayed.

Furthermore, according to the third embodiment, the image date iscorrected in the smooth area and the edge area separately from eachother. Hence, pixels can be corrected using parameters differingaccording to areas. Compared to the first and second embodiments,quality of the image represented by the corrected image data IMG′ can beimproved.

At least a portion of the image processing apparatus 10 a according tothe above-described embodiments may be composed of hardware or software.When at least a portion of the image processing apparatus 10 a iscomposed of software, a program for executing at least some functions ofthe image processing apparatus 10 a may be stored in a recording medium,such as a flexible disk or a CD-ROM, and a computer may read and executethe program. The recording medium is not limited to a removablerecording medium, such as a magnetic disk or an optical disk, but it maybe a fixed recording medium, such as a hard disk or a memory.

In addition, the program for executing at least some functions of theimage processing apparatus 10 a according to the above-describedembodiment may be distributed through a communication line (whichincludes wireless communication) such as the Internet. In addition, theprogram may be encoded, modulated, or compressed and then distributed bywired communication or wireless communication such as the Internet.Alternatively, the program may be stored in a recording medium, and therecording medium having the program stored therein may be distributed.

While certain embodiments have been described, these embodiments havebeen presented by way of example only, and are not intended to limit thescope of the inventions. Indeed, the novel methods and systems describedherein may be embodied in a variety of other forms; furthermore, variousomissions, substitutions and changes in the form of the methods andsystems described herein may be made without departing from the spiritof the inventions. The accompanying claims and their equivalents areintended to cover such forms or modifications as would fall within thescope and spirit of the inventions.

1. An image processing apparatus comprising: an image block generatorconfigured to enlarge an image block comprising a plurality of pixels togenerate an enlarged image block; a pixel extractor configured toextract a maximum pixel with a maximum pixel value and a minimum pixelwith a minimum pixel value from the image block; a correction parametercalculator configured to calculate a correction parameter comprising afirst difference and a second difference, the first difference being anabsolute value of a difference between a sample pixel value of a samplepixel to be corrected in the enlarged image block and the maximum pixelvalue, the second difference being an absolute value of a differencebetween the sample pixel value and the minimum pixel value; and acorrector configured to correct the enlarged image block using thecorrection parameter.
 2. The apparatus of claim 1, wherein the pixelextractor determines an objective area comprising an objective pixel tobe extracted in the image block, changes a pixel value of the objectivepixel by a tap filter, and extract the maximum pixel and the minimumpixel from the objective area.
 3. The apparatus of claim 1, wherein thepixel extractor divides the image block into an edge area and a smootharea based on degree of characteristic of the image block, extracts afirst maximum pixel comprising the maximum pixel value and a firstminimum pixel comprising the minimum pixel value in the edge area, andextracts a second maximum pixel comprising the maximum pixel value and asecond minimum pixel comprising the minimum pixel value in the smootharea.
 4. The apparatus of claim 3, wherein when at least one of a pixelvalue of the second maximum pixel and a pixel value of the secondminimum pixel is out of a predetermined range, the pixel extractorextracts at least one of the second maximum pixel and the second minimumpixel from the objective area to which an area comprising at least oneof the second maximum pixel and the second minimum pixel is, at leastone of the extracted second maximum pixel and the extracted secondminimum pixel with pixel values in the predetermined range.
 5. Theapparatus of claim 1, wherein the correction parameter calculatorcalculates the correction parameter comprising a vector functioncomprising a direction defined by magnitude relation between the firstdifference and the second difference and comprising degree defined by anabsolute value of a difference between the first difference and thesecond difference, and the corrector adds the correction parameter tothe sample pixel value.
 6. The apparatus of claim 5, wherein the vectorfunction is a monotone increasing function.
 7. The apparatus of claim 5,wherein the correction parameter calculator calculates the correctionparameter comprising a product of a first coefficient and the vectorfunction, the first coefficient defined by a third difference being anabsolute value of a difference between the maximum pixel value and theminimum pixel value.
 8. The apparatus of claim 7, wherein the firstcoefficient is a monotone increasing function.
 9. The apparatus of claim7, wherein the correction parameter calculator calculates the correctionparameter comprising a product of the first coefficient, a secondcoefficient and the vector function, the second coefficient defined bydegree of characteristic of the image block.
 10. The apparatus of claim9, wherein the correction parameter calculator determines the secondcoefficient based on attribute information included in the image block.11. The apparatus of claim 9, wherein the correction parametercalculator analyze the image block to detect the degree and determinesthe second coefficient based on the detected degree.
 12. The apparatusof claim 1, wherein when the corrected enlarged image block comprises apixel with a corrected pixel value out of a predetermined range, thecorrector changes the corrected pixel value into at least one of themaximum pixel value and the minimum pixel value.
 13. An image processingsystem comprising: an image block generator configured to enlarge animage block comprising a plurality of pixels to generate an enlargedimage block; a pixel extractor configured to extract a maximum pixelwith a maximum pixel value and a minimum pixel with a minimum pixelvalue from the image block; a correction parameter calculator configuredto calculate a correction parameter comprising a first difference and asecond difference, the first difference being an absolute value of adifference between a sample pixel value of a sample pixel to becorrected in the enlarged image block and the maximum pixel value, thesecond difference being an absolute value of a difference between thesample pixel value and the minimum pixel value; a corrector configuredto correct the enlarged image block using the correction parameter; anda display configured to display an image based on the corrected enlargedimage block.
 14. The system of claim 13, further comprising: an imagingapparatus configured to pick up the image of an object to generate imagedata comprising a plurality of pixels; and a video decoder configured todecode the image data to generate the image block.
 15. The system ofclaim 13, further comprising: a memory configured to store image data;and a video decoder configured to decode the image data to generate theimage block.
 16. The system of claim 13, further comprising: acommunicator apparatus configured to receive image data via a network;and a video decoder configured to decode the image data to generate theimage block.
 17. The system of claim 13, wherein the pixel extractordetermines an objective area comprising an objective pixel to beextracted in the image block, applies a tap filter to the objective areato change a pixel value of the objective pixel, and extract the maximumpixel and the minimum pixel from the objective area.
 18. The system ofclaim 13, wherein the pixel extractor divides the image block into anedge area and a smooth area based on degree of characteristic of theimage block, extracts a first maximum pixel comprising the maximum pixeland a first minimum pixel comprising the minimum pixel in the edge area,and extracts a second maximum pixel comprising the maximum pixel and asecond minimum pixel comprising the minimum pixel in the smooth area.19. The system of claim 18, wherein when at least one of the pixelextractor extracts a pixel value of the second maximum pixel and a pixelvalue of the second minimum pixel is out of a predetermined range, thepixel extractor extracts at least one of the second maximum pixel andthe second minimum pixel from the objective area to which an areacomprising at least one of the second maximum pixel and the secondminimum pixel is, at least one of the extracted second maximum pixel andthe extracted second minimum pixel with pixel values in the range.
 20. Amethod for processing image, the method comprising: enlarging an imageblock comprising a plurality of pixels to generate an enlarged imageblock; extracting a maximum pixel with a maximum pixel value and aminimum pixel with a minimum pixel value from the image block;calculating a correction parameter comprising a first difference and asecond difference, the first difference being an absolute value of adifference between a sample pixel value of a sample pixel to becorrected in the enlarged image block and the maximum pixel value, thesecond difference being an absolute value of a difference between thesample pixel value and the minimum pixel value; and correcting theenlarged image block using the correction parameter.